The Specific Heat of Non-conductors. 



45 



That the correction is a very necessary one is seen if 

 we calculate the above, ignoring C, when we obtain for ;r the 

 value 0'47i. About the same value for C, viz. "2°, was 

 obtained by Pape and Pfaundler, in a large series of 

 experiments made on various earths and salts. 



The results agree as well as can be expected, considering 

 the nature of the substance. From the mean of the best 

 experiments, shown in the following table, we obtain the 

 figure '480, which, with a possible variation of about 2%, may 

 be considered as the specific heat of caoutchouc : — 



Summary of Results. 

 Caoutchouc. 



Expt. 



W. 



K. 



M. 



mV. 



T. 



t. 



0. 



c. 



X. 



I. 



298*07 



6*1 



23'94 



•65 



95'3 



15-38 



18*28 



*I2 



-471 



2. 



298*46 



6*1 



18-82 



•68 



97*o 



14*84 



17-25 



•16 



•486 



3- 



295*4 



5-1 



i8-35 



I 01 



98*2 



14*32 



16-84 



-12 



•474 



4. 



293'3 



51 



19-55 



•85 



98-5 



15*01 



17-74 



*I2 



•483 



5- 



250*0 



4-0 



18*76 



•44 



98*0 



16-35 



19-18 



*I2 



•484 



6. 



298-3 



57 



41-28 



•06 



99-0 



18-72 



23-39 



-24 



-478 



Experiments with Oils. 



Some preliminary experiments have been made with the 

 oils distilled from Caoutchouc. The caoutchouc was dis- 

 tilled in an iron retort, and the vapours condensed, then the 

 liquid was shaken up with sulphuric acid, washed well with 

 water, and re-distilled into different fractions. The lightest 

 fraction — a pale yellow colour — was used, and as the oils are 

 all polymeric, the same results would be obtained from all 

 the fractions. The oils are isomeric with oil of turpentine, 



